1. Field of the Invention
The present invention relates to a planetary gear set for a transmission, and more particularly, to a technology of reducing noise generated from a planetary gear set, which are widely used in automatic transmissions.
2. Description of Related Art
FIG. 1 is a cross-sectional view showing the structure of an automatic transmission of the related art, in which torque is supplied from a torque converter 500 to a plurality of planetary gear sets 504 through a input shaft 502 and power is produced at various gear ratio generated by the planetary gear sets 504 and supplied to the driving wheels of a vehicle, by selectively operating a plurality of friction-driven elements.
In the automatic transmission having this configuration described above, planetary gear set 504 is composed of a sun gear, a carrier, and a ring gear, in which the carrier functions as an element that controls power input and output of planetary gear set 504 while providing shafts for pinion gears revolving and rotating between the sun gear and the ring gear.
Planetary gear set 504 generates noise in the operation, particularly, large noise is generated due to bad engagement and contact between the gears of planetary gear set 504.
It is difficult to set and maintain the size of the ring gear, pinion gear, and carrier such that all of the pinion gears is closely engaged with the ring gear at one time, in consideration the assemblage of planetary gear set 504.
That is, it is difficult to insert the carrier, with the pinion gears engaged with the ring gear, such that it is required to provide an assembly tolerance for smooth assembly, when the ring gear, pinion gears, and carrier are manufactured such that the carrier equipped with the pinion gears is inserted inside the ring gear and the pinion gears can be inserted in complete engagement at a plurality of positions of the ring gear.
However, the assembly tolerance described above makes it easy to combine the ring gear with the pinion gears, but it is difficult to maintain accurate and appropriate engagement between all the teeth of the ring gear and the pinion gears in the operation after they are combined. Therefore, the contact state between some teeth is deteriorated and this is a cause generating noise in the operation of planetary gear set 504, when rotation is made by large torque.
That is, as shown at the left side of FIG. 2, when a ring gear R and a pinion gear P are assembled with an assembly tolerance, the engagement between pinion gear P and ring gear R is deteriorated in large-torque rotation, as shown at the right side, which becomes a main cause for operational noise of planetary gear set 504.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.